1. Technical Field
The present disclosure relates to a photoalignment compound, a photoalignment composition, a display substrate having an alignment layer, and a method for manufacturing the display substrate. More particularly, the present disclosure relates to a photoalignment compound which is used in manufacturing an alignment layer of a liquid crystal display (LCD) device, a photoalignment composition, a display substrate having an alignment layer, and a method for manufacturing the display substrate.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) panel includes a first display substrate having a thin-film transistor (TFT) as a switching element to drive a pixel, a second display substrate facing the first display substrate, and a liquid crystal layer interposed between the first display substrate and the second display substrate. An image may be displayed on the LCD panel according to the light transmittance of liquid crystal material, which may change according to voltages.
An alignment layer is formed on inner portions of each of the first display substrate and the second display substrate because it may be difficult to obtain an ideal liquid crystal molecular arrangement by only disposing the liquid crystal material between the first display substrate and the second display substrate. The alignment layer may be formed by, for example, spreading a raw alignment material using a printing roller of an alignment layer printing apparatus on a base substrate and a rubbing process. For example, the raw alignment material may be a solution including a polyimide polymer.
However, static electricity may be generated by rubbing with a rubbing cloth during the rubbing process to form the alignment layer, and thus the first or second display substrates may be damaged by the static electricity. In addition, the first or second display substrates may be readily polluted and stained in the rubbing process, thereby decreasing display quality.
To prevent static electricity and improve display quality, a photoalignment process has been developed. For example, methods including spreading a photoalignment material on the base substrate followed by photodegrading, photoisomerizing, or photopolymerizing the photoalignment material using light have been developed. The reliability of the alignment layer using the photoalignment process may depend on, for example, thermal stability, optical stability, chemical stability, alignment stability, etc. Particularly, the alignment stability of the photoalignment material may be significant for aligning the liquid crystal molecules, which is a beneficial role of the alignment layer.
However, there is still a need in the art for a photoalignment compound capable of improving the reliability of manufacturing an alignment layer and the alignment stability of the liquid crystal molecule, a photoalignment composition, a display substrate having an alignment layer, and a method for manufacturing the display substrate. In addition, there is also a need in the art for a photoalignment compound in which the developments costs are decreased.